System of electric distribution



March 10, 1925. 1,529,325

(5. E. STEWART SYSTEM OF ELECTRIC DISTRIBUTION Filed Jan. 28, 1924Inventor: Glenn EStewarc,

H is Attorney.

Patented Mar. 10, 1925.

UNITED STATES 5,529,325 PATENT orrie.

GLENN E. STEZVART. OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO GENERALELECTRIC CQMPANY. A CORPORATION OF NEW YORK.

SYSTEM OF ELECTRIC DISTRIBUTION.

Application filed January 28, 1924. Serial No. 689,148.

To all whom it may concern:

Be it known that I, GLENN l5. Srnwaur. a citizen of the United States.residing at Philadelphia, in the county of Philadelphia. State ofPennsylvania, have invented ccr tain new and useful Improvements inSystems of Electric Distribution, of which the following is aspecification.

My invention relates to systems of electric distribution andparticularly to an improved arrangement for controlling the connectionbetween two electric circuits so that the connection cannot beestablished between them until the voltage of one of the circuitsexceeds the voltage of the other circuit by a predetermined amount.

My invention is of particular utility in automatic substations where itis necessary to connect a generator to a distribution circuit which maybeenergized at some other oint. In order to prevent the generator ii'omoperating as a motor after it is connected to the distribution circuit,it is necessary to provide suitable means for preventing the circuitbreaker, which is arranged to connect the generator to the distributioncircuit, from being closed until the generator voltage exceeds thecircuit voltage by a predetermined amount.

One object of my invention is to provide an improved arrangement forcontrolling the connection between two electric circuits in accordancewith the relative voltages of the two circuits, which is more sensitiveand more reliable in its operation than any of the arrangements usedheretofore for this purpose.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing and its scope will bepointed out in the appended claims.

Referring to the accompanying drawing which shows one embodiment of myinvention, 1 represents a direct current generator which is arranged tobe connected, by means of a suitable circuit breaker 2, to adistribution circuit 3 which is adapted to be energized at some otherpoint. As shown, one side of the distribution circuit is the ground, andthe circuit breaker 2 is arranged to connect one terminal of thegenerator to the ungrounded side of the distribution circuit, the otherterminal of the generator being permanently connected to ground. It isevident, however, that my invention is not limited to a grounded system,nor to having the circuit breaker between the ungrounded terminal andthe ungrounded side of the circuit. The distribution circuit is alsoshown as being adapted to be energized by another source 4 which isarranged to be connected to the distribution circuit by a circuitbreaker 5 which may be of any suitable type.

It is evident that in order for the generator l to supply current to thedistribution circuit when it is energized at some other point, thevoltage of the generator must be equal to the voltage of the circuit.Therefore, the voltage of the generator 1 should be higher than the linevoltage before the circuit breaker 2 is closed to connect the generatorto the line. For accomplishing this result, I provide a directionalrelay 7 which is so connected and arranged that, when the circuitbreaker 2 is open, the circuit of theclosing coil 6 of the circuitbreaker 2 is prevented from being closed until the voltage of thegenerator exceeds the line volta e by a predetermined value.

The directional relay 7 may be of any suitable type, but I prefer to usethe type of relay described and claimed in a copending application,Serial No. 482,630, filed July 5, 1.921, by H. W. Brown and assigned tothe same assignee as this application. This relay comprises an armature8 pivotally mounted within an operating winding 11 and between pairs ofpolar projections 16, 16 and 17, 17', of a magnetic structure 18 whichis energized by a magnetizing winding 12. The armature 8 tends to turnon its pivot in one direction or the other depending upon the directionof current in the operating winding 11, and is provided with a contact19 which is arranged to engage another contact 20 when the armature 8 ismoved in one direction. Therefore, it is obvious that when the currentin the operating winding 11 is in one direction with respect to thecurrent in the magnetizing winding 12, the contacts 19 and 20 we closedand when the current in the operating winding 11 is in the oppositedirection, the contacts 19 and 20 are open.

As shown in the drawing the contacts 19 and 20 are connected in theenergizing circuit of the closing coil 6 of the circuit breaker 2 sothat when the contacts 19 and 20 are closed, the circuit breaker closes.

In order that the relay 7 may Operate in response to the relativepotentials of the generator 1 and the distribution circuit 3 to controlthe closing of the circuit breaker 2 when it is open, the operatingwinding 11 is arranged to be connected in series with the generator andthe distributioncircuit and the magnetizing winding 12 is arranged to beenergized from a suitable source such as the generator 1 when thecircuit breaker is open.

When the circuit breaker is closed, it is desirable that the contacts 19and 20 of the relay 7 should be open so as to insure that these contactswil be open, when the circuit breaker opens, an, thereby prevent thecircuit breaker 2 from reclosing until the volt age of the generator ishigher than the voltage of the distribution circuit. lhereiore, it isdesirable to arrange the connections of the directional relay 7 so thatwhen the circuit breaker 2 closes the relay opens its contacts 19 and 20and maintains the contacts open until the circuit breaker is open andthe voltage of the generator 1 exceeds the voltage across thedistribution circuit by a predetermined amount. Since the characteristicof the relay 7 is such that after the contacts 19 and 20 are closed, theenergizetion of only the magnetizing winding 12 is sufiicient tomaintain the contacts 19 and 20 closed, it is necessary either to openthe circuits of both windings of the relay 7, or cause the current toreverse in one of them, after the circuit breaker 2 closes, in order tomake the relay open its contacts 19 and 20.

In the arrangement shown in the drawing, 1 have shown an improvedarrangement for accomplishing these desired results. The operating andmagnetizing windings 11 and 12 are permanently connected in seriesacross the distribution circuit 3 in such a manner that when currentflows from the ungroundthe current through the operating winding withrespect to the direction of the current in the magnetizing winding issuch that the armature 8 tends to turn on its pivot in a direction toopen the contacts 19 and 20. When the circuit breaker'2 is open, theauxiliary contacts 22 on the circuit breaker connect a point 23, whichis between the two windings 11 and 12 in the series circuit of thewindings, to the ungrounded tern iinal of the generator so that themagnetizing winding 12 is connected directly across the terminals of thegenerator 1 and the operating winding 11 is connected in series with theungrounded terminal of the generator and the ungrounded side of thedistribution circuit. This change in the conncctions of the windings 11and 12 does not change the direction of the current through themagnetizing winding 12 but the direction of the current through theoperating winding 1h depends upon the relative voltages of the generator1 and If, however, the generator voltage is higher than distributioncircuit voltage,'the current through the operating winding 11 flowsin-the opposite direction and when the voltage difference exceeds apredetermined value, depending upon the adjustment of the calibratingspring2l, the armature. 8 rotates on its pivot in a direction to closethe contacts 19 and 20 and complete the circuit of the closing coil 6 ofthe circuit breaker 2 so that the circuit breaker closes. The opening ofthe auxiliary contacts 22 on the circuit breaker 2, when the circuitbreaker closes, disconnects the point 23 from the ungrounded terminal ofthe generator 1 so that current againfiows from the ungrounded side ofthe distribution circuit 8 through the windings 11 and 12 in series toground. This current causes the relay 7 to open its contacts 19 and .20in the man ner heretofore described.

It will be apparent therefore that I have provided a simple arrangementof connections whereby the current through one of the windings of therelay 7 is reversed, when the circuit breaker closes. to cause the relayto open its contacts 19 and 20.

In order that the circuit of the closing coil 6 may be completed afterthe circuit breaker 2 closes and the relay 7 opens its contacts 19 and20,'the circuit breaker 2 is provided with auxiliary contacts 24 whichare closed when the circuit breaker is closed and i which complete acircuit in shunt around the contacts 19 and 20. The circuit of theclosing coil 6 may also include contacts of suitable protective devicessuch as the contacts 25 of an overload relay 26, so that circuit breakermay be controlled by other conditions than the relative voltages of thegencratoriand the distribution circuit.

It may also be desirable to provide in the connection between the point23 and the ungrounded terminal of the generator 1, a suitable switch 28,which may be either manually or automatically controlled, so that thegenerator may be entirely disconnected from the distribution circuitSunder certain conditions.

While I have shown my invention in. connection with an arrangement forcontrollin the connection between a generator and a distributioncircuit, it is obvious that is not limited to such an arrangement but isapplicable to controlling the connection between any two sources orindependently energized circuits. 7

Furthermore, while I have shown and described only one embodiment of myinvention, I do not desire to be limited thereto, but seek to cover inthe appended claims all those modifications that fall within the truespirit and scope of my invention.

\Vhat I claim as new and desire to secure by Letters Patent of theUnited States, is

1. In combination, two electric circuits adapted to be energizedindependently of each other, a circuit breaker for connecting saidcircuits together, a directional relay for controlling the closing ofsaid circuit breaker having two windings arranged to be connected whensaid circuit breaker is open so that the currents flow through saidwindings in the proper direction to operate said relay to effect theclosing of said circuit breaker when the voltage of a predetermined oneof said circuits exceeds the voltage of the other circuit, and meanscontrolled by said circuit breaker for causing the current in one of thewindings of said relay to reverse when said circuit breaker closes.

2. In combination, two electric circuits adapted to be energizedindependently of each other, a circuit breaker for connecting saidcircuits together, a directional relay for controlling the closing ofsaid circuit breaker having two windings arranged to be connected acrossone of said circuits when said circuit breaker is closed, and meanscontrolled by said circuit breaker for connectin one of said windings inseries with said clrcuits when said circuit breaker is open.

3. In combination, two electric circuits adapted to be energizedindependently of each other, a circuit breaker for connecting saidcircuits together, a directional relay for controlling the closing ofsaid circuit breaker having two windings arranged to be connected acrossone of the circuits when said circuit breaker is closed, and meanscontrolled by said circuit breaker for connecting one of said windingsacross the other one of said circuits and the other one of said windingsin ser es with said circuits when said circuit breaker is open.

4. In combination, a source of current, an electric circuit, adapted tobe energized at more than one point, a circuit breaker arranged toconnect said source to said electric circuit, a directional relay forcontrolling said circuit breaker having two windings connected acrosssaid electric circuit when eircuitbreaker is closed and arranged so thatthe current through one of said windings is in such a direction withrespect to the direction of the current in the other winding that saidrelay is ineffective to close said circuit breaker, and means forconnecting one of said windings in series with said source and electriccircuit when said circuit breaker is open so that the currents in saidwindings are in the proper direction to cause the relay to effect theclosing of said circuit breaker when the voltage of the source exceedsthe voltage of the electric circuit.

5. In combination, two electric circuits adapted to be energizedindependently of each other, a circuit breaker for connecting saidcircuits together, a closing coil for said circuit breaker, a circuitfor said closing coil, a directional relay for controlling said closingcoi ircuit having two windings arranged to be connected in a seriescircuit across one of-said electric circuits in such a manner that thedirection of current through one of said windings is such with respectto the direction of the current through the other winding as to causesaid relay to maintain said closing coil circuit open, and meansoperative when said circuit breaker is open for establishing aconnection between said series circuit and one of said electric circuitswhereby the currents through both of the windings of said relay are inthe proper direction to cause the relay to complete the closing coilcircuit of said circuit breaker when the voltage of one of said electriccircuits exceeds the voltage of the other electric circuit by apredetermined amount.

In witness whereof, I have hereunto set my hand this 24th day of J anuar1924.

GLENN E. STE ART.

